Steps to reproduce:

1. Open any item prototype configuration (whose item type supports update interval) or create new item prototype.
2. Set any LLD macro to Update interval field, e.g. {#INTERVAL}
3. Click submit (Update/Add) button.

Result (in >= 7.0):
Error message "Incorrect value for field "delay": a time unit is expected." is shown and item prototype is not updated.
Expected (as in < 7.0):
LLD macro is set as update interval of item prototype.

Additional info:
This issue appeared in 7.0 where modal windows for item prototype configuration was introduced. Using LLD macro as update interval should be supported {}according to the documentation. I used this in 6.0 and retested in 6.4. It works in both versions.